The technology used in modern energy saving lighting devices uses mercury as one of the active components. As mercury harms the environment, extensive research is done to overcome the complicated technical difficulties associated with energy saving, mercury-free lighting.
An approach used for solving this problem is by using field emission light source technology. Field emission is a phenomenon which occurs when an electric field proximate to the surface of an emission material narrows a width of a potential barrier existing at the surface of the emission material. This allows a quantum tunneling effect to occur, whereby electrons cross through the potential barrier and are emitted from the material.
In prior art devices, a cathode is arranged in an evacuated chamber, having for example glass walls, wherein the chamber on its inside is coated with an anode electrically conductive layer. Furthermore, a light emitting layer is deposited on the anode conductive layer. When a potential difference is applied between the cathode and the anode conductive layer, electrons are emitted from the cathode, and accelerated towards the anode conductive layer. As the electrons strike the light emitting layer, they cause it to emit photons, a process referred to as cathodoluminescence, which is different from photoluminescence which is employed in conventional fluorescent lighting devices, such as conventional fluorescent tubes.
Such a device is disclosed in U.S. Pat. No. 6,573,643, wherein the anode conductive layer for example can be composed of indium-tin oxide and the light emitting layer is composed of phosphorescent material. This phosphorescent material receives electrons from a cathode and emits photons at a visible wavelength.
Such a phosphorescent material that receives electrons and emits photons at a visible wavelength is very expensive and difficult to manufacture, resulting in expensive lighting devices.
It is therefore an object of the present invention to provide a novel and improved field emission light source that provides a solution to some of the above mentioned problems.